Certain carboxy substituted 4-oxo-1,4-dihydropyridazines and carboalkoxy substituted 4-oxo-1,4-dihydropyridazines are known in the art to have plant gametocidal activity as disclosed in U.S. Pat. Nos. 4,707,181 issued on Aug. 24, 1982 to T. T. Fujimoto and 4,732,603 issued on Mar. 22, 1988 to D. R. Patterson. These patents disclose preparing these compounds by reacting a 2-phenylhydrazono-3-oxoglutarate with an organic acid chloride in the presence of a Grignard reagent (isopropyl magnesium chloride). This process resulted in low yields of product and involved the use of the reactive and expensive Grignard reagent. There still is a need in the art for a more efficient and commercially viable process for making substituted 4-oxo-1,4-dihydropyridazines.